Methods for a user equipment device to request MAC messages from a base station

ABSTRACT

In order to perform a RACH-less handover from a source base station to a target base station, a UE device generates a request that the target base station is to send a Media Access Control (MAC) message to the UE device. The request can be sent with a Radio Resource Control (RRC) Connection Reconfiguration Complete message. Alternatively, an RRC message sent from a UE device functions as an implicit request that the target base station is to send a MAC message to the UE device. The request can also be configured to specify a particular MAC Control Element that the target base station should send. The target base station transmits the requested MAC message, along with TA information, if required. The UE device determines when the handover has been completed, based at least partially on when the requested MAC message is received from the target base station.

CLAIM OF PRIORITY

The present application claims priority to Provisional Application No.62/406,721, entitled “METHOD OF UE REQUESTS FOR MAC MESSAGES FROM ANENB”, filed Oct. 11, 2016, and to Provisional Application No.62/407,243, entitled “METHODS FOR A UE TO REQUEST MAC MESSAGES FROM ANENB”, filed Oct. 12, 2016, both of which are assigned to the assigneehereof and hereby expressly incorporated by reference in their entirety.

FIELD

This invention generally relates to wireless communications and moreparticularly to user equipment devices requesting messages from basestations.

BACKGROUND

In conventional systems, a handover of a user equipment (UE) device froma source base station (e.g., source eNB) to a target base station (e.g.,target eNB) involves the source base station transmitting a HandoverRequest message to the target base station (e.g., to initiate ahandover) and the target base station transmitting a message inresponse. The source base station signals target base station uplinkresources to the UE device, which utilizes the uplink resources for aRandom-Access Channel (RACH) procedure. After the UE device is handedover to the target base station, the UE device transmits an uplinksignal to the target base station as part of the RACH procedure. Thetarget base station uses the uplink signal received from the UE deviceto calculate a Timing Advance (TA), which is needed in order for the UEdevice's uplink transmissions to be synchronized to the target basestation after handover. The target base station signals the TA in theRandom Access Response (RAR) message, along with uplink resources neededfor the UE device to obtain uplink access to the target base station aspart of the RACH procedure. The UE device determines when the handoverprocedure is completed for the UE device, based upon when the UE devicereceives the RAR message.

SUMMARY

In order to perform a handover from a source base station to a targetbase station, where the handover procedure does not include the RACHprocedure (RACH-less handover), a UE device generates a request that thetarget base station is to send a Media Access Control (MAC) message tothe UE device. In some examples, the request can be sent along with aRadio Resource Control (RRC) Connection Reconfiguration Completemessage. In other examples, an RRC message, such as an RRC ConnectionReconfiguration Complete message sent from a UE device to the targetbase station, functions as an implicit request that the target basestation is to send a MAC message to the UE device. The request can alsobe configured to specify a particular MAC Control Element that thetarget base station should send in response to receiving the request.Upon receipt of the request, the target base station transmits therequested MAC message to the UE device, along with TA information, ifrequired. The UE device determines when the handover has been completed,based at least partially on when the requested MAC message is receivedfrom the target base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system for an example inwhich a UE device requests that a base station transmits a MAC messageto the UE device.

FIG. 2A is a block diagram of an example of the base stations shown inFIG. 1.

FIG. 2B is a block diagram of an example of the UE device shown in FIG.1.

FIG. 3A is a messaging diagram of an example of the messages exchangedbetween the various system components shown in FIG. 1.

FIG. 3B is block diagram of an example of a MAC Protocol Data Unitstructure.

FIG. 4 is a flowchart of an example of a method in which a UE devicerequests that a base station transmits a MAC message to the UE device.

DETAILED DESCRIPTION

The Timing Advance (TA) provided by a target base station to a UE deviceduring a handover in conventional systems is needed in order for the UEdevice's uplink transmissions to be synchronized to the target basestation after handover. If the uplink transmissions are not properlysynchronized to the target base station, the target base station willnot be able to detect and decode the transmissions. However, onedrawback of conventional systems is that the TA determination step isperformed after the handover procedure has been initiated, whichunnecessarily increases the amount of time required to complete thehandover procedure in examples when the TA does not need to bedetermined during a handover.

RACH-less handovers can be used in examples when the TA does not need tobe determined during a handover, in order to reduce the time required tocomplete the handover procedure. As used herein, the term “RACH-lesshandover” refers to skipping the transmission of the Random-AccessChannel (RACH) by the user equipment (UE) device to the target basestation (e.g., target eNB) during handover, which significantly improvesthe delay for the handover procedure since the RACH procedure is asubstantial part of the handover delay. However, if the RACH procedureis not performed, an alternative method is needed to determine the TAfor the UE device so that the target base station is able to detect anddecode uplink transmissions from the UE device. Thus, an alternativemethod is needed to provide information, such as the TA and the uplinkgrant, which are usually included in the Random Access Response (RAR)message sent by the target base station in response to receiving theRACH message from the UE device. In addition, the alternative methodmust provide a way for the UE device to be able to determine when ahandover of the UE device has been successfully completed, which isdetermined by receiving the RAR message in conventional systems.

The examples described herein involve transmitting an uplink grant foran uplink transmission to the target base station in a Radio ResourceControl (RRC) Connection Reconfiguration message that is sent by thesource base station to the UE device. Upon receipt of the RRC ConnectionReconfiguration message, the UE device generates a request that thetarget base station is to send a MAC message to the UE device. The UEdevice transmits the request using the uplink grant received in the RRCConnection Reconfiguration message.

In some examples, the request can be sent along with an RRC ConnectionReconfiguration Complete message, and in other examples, the RRCConnection Reconfiguration Complete message, itself, serves as animplicit request. Upon receipt of the request, the target base stationtransmits the requested MAC message to the UE device, along with TAinformation, if required. The UE device determines when the handover hasbeen completed, based at least partially on when the requested MACmessage is received from the target base station. Any unnecessaryinformation received in the MAC message may be discarded by the UEdevice.

FIG. 1 is a block diagram of a communication system for an example inwhich a UE device requests that a base station transmits a MAC messageto the UE device. The communication system 100 is part of a radio accessnetwork (not shown) that provides various wireless services to UEdevices that are located within the respective service areas of thevarious base stations that are part of the radio access network.

In the interest of clarity and brevity, communication system 100 isshown as having only source base station 102 and target base station104. However, in other examples, communication system 100 could have anysuitable number of base stations. In the example of FIG. 1, at least aportion of the service area (cell) for source base station 102 isrepresented by cell 108, and at least a portion of the service area(cell) for target base station 104 is represented by cell 112. Cells108, 112 are represented by ovals, but a typical communication system100 would have a plurality of cells, each having variously shapedgeographical service areas. Base stations 102, 104, sometimes referredto as eNodeBs or eNBs, communicate with the wireless user equipment (UE)device 106 by respectively transmitting downlink signals 110, 114 to UEdevice 106. Base stations 102, 104 receive uplink signals 118, 120transmitted from the UE device 106. The UE device 106 is any wirelesscommunication device such as a mobile phone, a transceiver modem, apersonal digital assistant (PDA), a tablet, or a smartphone, forexample.

Base stations 102, 104 are connected to the network through a backhaul(not shown) in accordance with known techniques. As shown in FIG. 2A,source base station 102 comprises controller 204, transmitter 206, andreceiver 208, as well as other electronics, hardware, and code. AlthoughFIG. 2A specifically depicts the circuitry and configuration of sourcebase station 102, the same base station circuitry and configuration isutilized for target base station 104 in communication system 100. Thebase station 102 is any fixed, mobile, or portable equipment thatperforms the functions described herein. The various functions andoperations of the blocks described with reference to the base station102 may be implemented in any number of devices, circuits, or elements.Two or more of the functional blocks may be integrated in a singledevice, and the functions described as performed in any single devicemay be implemented over several devices.

For the example shown in FIG. 2A, the base station 102 may be a fixeddevice or apparatus that is installed at a particular location at thetime of system deployment. Examples of such equipment include fixed basestations or fixed transceiver stations. In some situations, the basestation 102 may be mobile equipment that is temporarily installed at aparticular location. Some examples of such equipment include mobiletransceiver stations that may include power generating equipment such aselectric generators, solar panels, and/or batteries. Larger and heavierversions of such equipment may be transported by trailer. In still othersituations, the base station 102 may be a portable device that is notfixed to any particular location. Accordingly, the base station 102 maybe a portable user device such as a UE device in some circumstances.

The controller 204 includes any combination of hardware, software,and/or firmware for executing the functions described herein as well asfacilitating the overall functionality of the base station 102. Anexample of a suitable controller 204 includes code running on amicroprocessor or processor arrangement connected to memory. Thetransmitter 206 includes electronics configured to transmit wirelesssignals. In some situations, the transmitter 206 may include multipletransmitters. The receiver 208 includes electronics configured toreceive wireless signals. In some situations, the receiver 208 mayinclude multiple receivers. The receiver 208 and transmitter 206 receiveand transmit signals, respectively, through an antenna 210. The antenna210 may include separate transmit and receive antennas. In somecircumstances, the antenna 210 may include multiple transmit and receiveantennas.

The transmitter 206 and receiver 208 in the example of FIG. 2A performradio frequency (RF) processing including modulation and demodulation.The receiver 208, therefore, may include components such as low noiseamplifiers (LNAs) and filters. The transmitter 206 may include filtersand amplifiers. Other components may include isolators, matchingcircuits, and other RF components. These components in combination orcooperation with other components perform the base station functions.The required components may depend on the particular functionalityrequired by the base station.

The transmitter 206 includes a modulator (not shown), and the receiver208 includes a demodulator (not shown). The modulator modulates thesignals to be transmitted as part of the downlink signals 110 and canapply any one of a plurality of modulation orders. The demodulatordemodulates any uplink signals 118 received at the base station 102 inaccordance with one of a plurality of modulation orders.

Returning to FIG. 1, the communication system 100 provides variouswireless services to UE device 106 via base stations 102, 104. For theexamples herein, the communication system 100 operates in accordancewith at least one revision of the 3rd Generation Partnership ProjectLong Term Evolution (3GPP LTE) communication specification. UE device106 is initially served by source base station 102 and, thus, receivesdownlink signals 110 via antenna 212 and receiver 214, as shown in FIG.2B. Besides antenna 212 and receiver 214, UE device 106 furthercomprises controller 216 and transmitter 218, as well as otherelectronics, hardware, and code. UE device 106 is any fixed, mobile, orportable equipment that performs the functions described herein. Thevarious functions and operations of the blocks described with referenceto UE device 106 may be implemented in any number of devices, circuits,or elements. Two or more of the functional blocks may be integrated in asingle device, and the functions described as performed in any singledevice may be implemented over several devices.

The controller 216 includes any combination of hardware, software,and/or firmware for executing the functions described herein as well asfacilitating the overall functionality of a UE device. An example of asuitable controller 216 includes code running on a microprocessor orprocessor arrangement connected to memory. The transmitter 218 includeselectronics configured to transmit wireless signals. In some situations,the transmitter 218 may include multiple transmitters. The receiver 214includes electronics configured to receive wireless signals. In somesituations, the receiver 214 may include multiple receivers. Thereceiver 214 and transmitter 218 receive and transmit signals,respectively, through antenna 212. The antenna 212 may include separatetransmit and receive antennas. In some circumstances, the antenna 212may include multiple transmit and receive antennas.

The transmitter 218 and receiver 214 in the example of FIG. 2B performradio frequency (RF) processing including modulation and demodulation.The receiver 214, therefore, may include components such as low noiseamplifiers (LNAs) and filters. The transmitter 218 may include filtersand amplifiers. Other components may include isolators, matchingcircuits, and other RF components. These components in combination orcooperation with other components perform the UE device functions. Therequired components may depend on the particular functionality requiredby the UE device.

The transmitter 218 includes a modulator (not shown), and the receiver214 includes a demodulator (not shown). The modulator can apply any oneof a plurality of modulation orders to modulate the signals to betransmitted as part of the uplink signals 118, which are shown inFIG. 1. The demodulator demodulates the downlink signals 110, 114 inaccordance with one of a plurality of modulation orders.

At the beginning of operation of the example shown in FIG. 1, the UEdevice 106 is being served by source base station 102. Thus, uponreceipt of the downlink signals 110, the UE device 106 demodulates thedownlink signals 110, which yields encoded data packets that containdata pertaining to at least one of the wireless services that the sourcebase station 102 is providing to the UE device 106. The UE device 106decodes the encoded data packets, using controller 216, to obtain thedata.

When any one or more criteria are met for source base station 102 tohand the UE device 106 over to target base station 104, source basestation 102 transmits a handover request, via communication link 116, totarget base station 104. The handover criteria may include, for example,radio congestion at source base station 102, poor/deteriorating signalquality for the uplink/downlink signals for UE device 106, and/orunderutilization of available resources by target base station 104.However, any other suitable criteria could be used.

Regardless of the criteria used, the source base station 102 cantransmit the handover request to target base station 104 via a wired(e.g., X2) or a wireless communication link. If the transmission iswireless, source base station 102 uses transmitter 206 and antenna 210to transmit the UE device radio transmission configuration information,and target base station 104 receives the wireless transmission of thehandover request via antenna 210 and receiver 208. The transmission ofthe handover request to the target base station 104 is represented inFIG. 3A by signal 302.

If the target base station 104 agrees to the handover, the target basestation 104 sends a handover request acknowledgement message to thesource base station 102 via communication link 116, which can be a wiredconnection or a wireless connection. The handover requestacknowledgement message includes configuration information to be sent tothe UE device 106 to be used for accessing the target base station 104.The transmission of the handover request acknowledgement is representedin FIG. 3A by signal 304. Upon receipt of the handover requestacknowledgement, the source base station 102 transmits a Radio ResourceControl (RRC) Connection Reconfiguration message to the UE device 106.The RRC Connection Reconfiguration message includes uplink grantinformation, which the UE device 106 will utilize to send an RRCConnection Reconfiguration Complete message to the target base station104 once the RRC Connection Reconfiguration is complete. Thetransmission of the RRC Connection Reconfiguration message isrepresented in FIG. 3A by signal 306.

Upon receipt of the RRC Connection Reconfiguration message, the UEdevice 106 generates a request that the target base station 104transmits a Media Access Control (MAC) message to the UE device 106. Insome examples, the request comprises a Logical Channel Identifier (LCID)located in a subheader of a MAC Protocol Data Unit (PDU) that will betransmitted to the target base station 104. FIG. 3B shows an example ofa MAC PDU structure 320, which comprises a MAC header 322 and a MACpayload 324. The MAC header 322 comprises one or more subheaders 326that identify the type of information contained in the MAC payload 324.There is a subheader 326 associated with each entry in the MAC payload324. As can be seen in FIG. 3B, the first part of the MAC payload 324contains one or more MAC Control Elements 328 that are followed by oneor more MAC Service Data Units (SDUs) 330. The MAC SDUs include controldata, such as an RRC message, and user data. For the example shown inFIG. 3B, subheader 1 is associated with MAC Control Element 328, andsubheader 2 is associated with MAC SDU 330.

In some examples, the LCID, itself, is defined to request that thetarget base station 104 transmits a specific MAC Control Element, suchas a UE Contention Resolution Identity MAC Control Element, to the UEdevice 106. For these examples, only the LCID located in a subheader(e.g., subheader 1) is used to request a specific MAC Control Element orother MAC message, and no payload information is needed for the request.However, the request may be transmitted in a same MAC PDU 320 thatcontains a subheader (e.g., subheader 2) and a corresponding MAC SDU 330that includes an RRC Connection Reconfiguration Complete message. Inother examples, an RRC message, such as the RRC ConnectionReconfiguration Complete message is used to implicitly request that thetarget base station 104 is to transmit a specific MAC message. In stillother examples, regardless of the nature of the request, the request isthat the target base station 104 is to transmit a Random Access Response(RAR) message to the UE device 106.

Alternatively, the LCID can be a generic MAC Command Request, indicatingthat a MAC Control Element located in the MAC payload 324 identifies therequested command. For example, the LCID, which is included in asubheader 326 of the MAC PDU 320, is set to the MAC Command Requestvalue, and the specific MAC Control Element or MAC message beingrequested (e.g., UE Contention Resolution Identity or RAR) is identifiedby a value located in a MAC SDU 330 that corresponds with the subheaderthat contains the MAC Command Request LCID. The request may also betransmitted in a same MAC PDU 320 that contains a subheader 326 and acorresponding MAC SDU 330 that includes an RRC ConnectionReconfiguration Complete message.

For the examples described herein, MAC messages contain controlinformation that originates and terminates in peer MAC layer (Layer 2)protocol entities, such as specified in the 3rd Generation PartnershipProject Long Term Evolution (3GPP LTE) MAC specification, for example,and includes MAC messages, such as the Random Access Response (RAR)message, as well as MAC Control Elements. Radio Resource Control (RRC)messages contain control information that originates and terminates inpeer RRC layer (Layer 3) protocol entities. RRC layer messages arehigher layer messages with respect to MAC layer messages.

As described above, in some examples, the request is included in an RRCmessage, such as a Radio Resource Control (RRC) ConnectionReconfiguration Complete message. In some examples, an implicit requestfor the target base station 104 to send a MAC message is based on thetarget base station 104 receiving an RRC message and the nature of thecurrent procedure, such as an ongoing RACH-less handover. For example,in response to the UE device 106 sending an RRC ConnectionReconfiguration Complete message without including a RAR request messagein the MAC layer, the target base station 104 sends a RAR message to theUE device 106 based on receiving an RRC Connection ReconfigurationComplete message specifically during a RACH-less handover procedure, inaccordance with specified behavior, such as that defined in an industrystandard specification. In other examples, when the UE device 106 sendsa specific RRC message to the target base station 104, the target basestation 104 sends a specific MAC message, based on receiving the RRCmessage and the nature of the specific procedure (e.g., during aRACH-less handover procedure).

Regardless of the format of the request that the target base station 104is to transmit a MAC message, the UE device 106 transmits, viatransmitter 218 and antenna 212, the request to the target base station104 in an uplink transmission 120. As described above, in some examples,the request and the RRC Connection Reconfiguration Complete message maybe transmitted at the same time or at different times in separatemessages. In these examples, the transmission of the RRC ConnectionReconfiguration Complete message is represented in FIG. 3A by signal308, and the transmission of the request to the target base station 104is represented in FIG. 3A by signal 310. However, in other examples, thetransmission 310 of the request also includes the RRC ConnectionReconfiguration Complete message, and in other examples, the RRCConnection Reconfiguration Complete message, itself, functions as animplicit request.

The target base station 104 receives the request via antenna 210 andreceiver 208. Upon receipt of the request, the target base station 104utilizes controller 204 to generate a MAC message in accordance with thereceived request. More specifically, in some examples, the target basestation 104 generates a MAC message that contains the specific MACControl Element indicated in the request from the UE device 106. Forexample, if the request was for a UE Contention Resolution Identity MACControl Element, then the target base station 104 would generate a MACmessage containing a UE Contention Resolution Identity MAC ControlElement. Likewise, if the request was an explicit or an implicit requestfor a RAR, then the target base station 104 would generate a MAC messagecontaining a RAR.

The target base station 104 transmits, via transmitter 206 and antenna210, the MAC message containing the requested MAC message (e.g., a UEContention Resolution Identity MAC Control Element or a RAR) to the UEdevice 106. The transmission of the MAC message is represented in FIG.3A by signal 312. The UE device 106 receives the MAC message via antenna212 and receiver 214. Based at least partially upon when the UE device106 receives the requested MAC message, the UE device 106 usescontroller 204 to determine when the handover procedure (e.g., fromsource base station 102 to target base station 104) is completed for theUE device 106.

FIG. 3A is a messaging diagram of an example of the messages exchangedbetween the various system components shown in FIG. 1. In this example,the source base station 102 transmits a handover request to target basestation 104, via signal 302. In response, target base station 104transmits a handover request acknowledgement to the source base station102 via signal 304. Upon receipt of the handover requestacknowledgement, the source base station transmits an RRC ConnectionReconfiguration message to the UE device 106, which is represented bysignal 306. As mentioned above, the RRC Connection Reconfigurationmessage may contain uplink grant information required by the UE device106 as part of the handover to target base station 104.

Upon receipt of the RRC Connection Reconfiguration message, the UEdevice 106 generates a request that the target base station 104 is totransmit a MAC message to the UE device 106, as discussed above. The UEdevice 106 transmits the request to the target base station 104 in anuplink transmission 120. As described above, in some examples, therequest and the RRC Connection Reconfiguration Complete message may betransmitted as separate messages. In these examples, the transmission ofthe RRC Connection Reconfiguration Complete message is represented bysignal 308, and the transmission of the request to the target basestation 104 is represented by signal 310. However, in other examples,the transmission 310 of the request also includes the RRC ConnectionReconfiguration Complete message.

Upon receipt of the request, the target base station 104 generates thespecific MAC message indicated in the request from the UE device 106.The target base station 104 transmits the requested MAC message (e.g., aUE Contention Resolution Identity MAC Control Element or a RAR) to theUE device 106. In some examples, the MAC message also contains the TAinformation needed for the UE device 106 to synchronize its uplinktransmissions to the target base station after handover. Thetransmission of the MAC message is represented by signal 312.

FIG. 4 is a flowchart of an example of a method in which a UE devicerequests that a base station transmits a MAC message to the UE device.The method 400 begins at step 402 with generating, at UE device 106, arequest that target base station 104 is to transmit, to the UE device106, a specific MAC message. At step 404, the UE device 106 transmitsthe request to the target base station 104 in an uplink transmission. Atstep 406, in response to receiving the request, the target base station104 generates the requested MAC message and transmits the requested MACmessage to the UE device 106. At step 408, the UE device 106 determineswhen the handover procedure (e.g., from source base station 102 totarget base station 104) is completed for the UE device 106, based atleast partially upon when the UE device 106 receives the requested MACmessage.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

The invention claimed is:
 1. A method comprising: in a Random-Access Channel (RACH)-less handover procedure of a user equipment (UE) device from a source base station to a target base station, generating, at the UE device, a request that the target base station transmits a Media Access Control (MAC) message to the UE device, wherein the request is for a UE Contention Resolution Identity MAC Control Element; and transmitting the request to the target base station in an uplink transmission.
 2. The method of claim 1, wherein the request comprises a Logical Channel Identifier (LCID).
 3. The method of claim 1, wherein the request comprises a request for a Random Access Response (RAR).
 4. The method of claim 1, wherein the request comprises a request for a specific MAC Control Element.
 5. The method of claim 1, wherein the request comprises a message that conforms to a protocol layer that is higher than a MAC protocol layer.
 6. The method of claim 5, wherein the request further comprises a Radio Resource Control (RRC) Connection Reconfiguration Complete message.
 7. The method of claim 1, further comprising: in response to receiving the request, transmitting the requested MAC message to the UE device.
 8. The method of claim 7, further comprising: determining, by the UE device, when a handover procedure is completed for the UE device, based at least partially upon when the UE device receives the requested MAC message.
 9. The method of claim 1, wherein generating the request that the target base station transmits the MAC message to the UE device is performed in response to the UE device receiving a Radio Resource Control (RRC) Connection Reconfiguration message containing an uplink grant, the request transmitted to the target base station using the uplink grant.
 10. A method comprising: in a Random-Access Channel (RACH)-less handover procedure of a user equipment (UE) device from a source base station to a target base station, transmitting, at the UE device, control information to the target base station, the RACH-less handover procedure where the UE skips transmitting a RACH to the target base station; and in response to sending, at the UE device, the control information, receiving, at the UE device, UE Contention Resolution Identity Media Access Control (MAC) Control Element sent from the target base station.
 11. A system comprising: a user equipment (UE) device comprising: a controller configured to, in a Random-Access Channel (RACH)-less handover procedure of the UE device from a source base station to a target base station, generate a request that the target base station transmits a Media Access Control (MAC) message to the UE device, wherein the request is for a UE Contention Resolution Identity MAC Control Element; and a transmitter configured to transmit the request to the target base station in an uplink transmission.
 12. The system of claim 11, wherein the request comprises a Logical Channel Identifier (LCID).
 13. The system of claim 11, wherein the request comprises a request for a Random Access Response (RAR).
 14. The system of claim 11, wherein the request comprises a request for a specific MAC Control Element.
 15. The system of claim 11, wherein the request comprises a message that conforms to a protocol layer that is higher than a MAC protocol layer.
 16. The system of claim 15, wherein the request further comprises a Radio Resource Control (RRC) Connection Reconfiguration Complete message.
 17. The system of claim 11, wherein the target base station comprises a transmitter configured to transmit a MAC message to the UE device, in response to receiving the request for the MAC message.
 18. The system of claim 11, wherein the controller of the UE device is further configured to determine when a handover procedure is completed for the UE device, based at least partially upon when the UE device receives the requested MAC message.
 19. The method of claim 10, wherein the control information comprises a Radio Resource Control (RRC) Connection Reconfiguration Complete message.
 20. The method of claim 19, further comprising: in response to receiving, at the target base station, the control information sent from the UE device, sending, at the target base station, the UE Contention Resolution Identity MAC Control Element to the UE device.
 21. The method of claim 19, further comprising: in response to receiving, at the UE device, the UE Contention Resolution Identity MAC Control Element sent from the target base station, completing the RACH-less handover procedure.
 22. A method comprising: in a Random-Access Channel (RACH)-less handover procedure of a user equipment (UE) device from a source base station to a target base station, receiving, at the target base station, control information sent from the UE device, the RACH-less handover procedure where the UE skips transmitting a RACH to the target base station; and in response to receiving, at the target base station, the control information sent from the UE device, sending, at the target base station, the UE Contention Resolution Identity MAC Control Element to the UE device.
 23. The method of claim 22, wherein the control information comprises a Radio Resource Control (RRC) Connection Reconfiguration Complete message. 